Could Probiotics Replace Prozac?

Depression is a complex disease, but new research on mice is promising.

By Tom Jacobs

(Photo: Reymark Franke/Unsplash)

Not that long ago, people suffering from depression were dismissively told “It’s all in your head.” Newly published research suggests such comments are not only insensitive, but inaccurate.

At least part of the problem, in fact, may be in your gut.

University of Virginia researchers report stressed-out mice are lacking in lactobacillus, a common probiotic bacteria. Simply replacing it in their diets largely reversed the animals’ symptoms of anxiety and depression.

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Given that lactobacillus is found in many yogurts, this raises the tantalizing possibility of an easily available and inexpensive antidepressant might just be sitting in your supermarket’s dairy case.

“The big hope for this kind of research,” said lead researcher Alban Gaultier, “is that we won’t need to bother with complex drugs and side effects when we can just play with the microbiome” — the collection of microbes that call our bodies home.

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In the study, published in the journal Scientific Reports, a group of mice were subjected to a series of acute stressors, including “restraint, loud white noise, crowded housing, (and exposure to a) strobe light,” as well as lower-level, overnight stressors such as “repeated cage changes” and wet bedding.

Anxiety was measured by the extent to which an animal shredded its nestlet. Despair was measured using a “forced swim test,” where remaining immobile and floating (rather than attempting to swim their way out of a water-filled cylinder) is seen as a sign of depression.

The researchers examined the animals’ gut bacteria before and after they were subjected to such stress, and found depleted levels of lactobacillus following the traumatic experiences. Restoring the level of this gut bacteria “correlated directly with the behavior of these mice,” said co-author Ioana Marin, greatly reducing their “behavioral abnormalities.”

What’s behind this effect? The researchers report low levels of lactobacillus were associated with increased levels of the blood metabolite kynurenine, which has been implicated in depression. If that is indeed the mechanism behind these findings, this treatment should theoretically work on humans as well as mice, although more research will obviously be needed.

Before rushing out to the health-food store, it’s important to note that scientists are divided on the benefits of commonly available probiotic supplements. While we all love quick fixes, a healthy, balanced diet — including yogurt products — is probably the best way of ensuring an optimum balance of gut bacteria.

The results follow by just one month a Swedish study that reports mice suffering from Alzheimer’s have a different composition of gut bacteria compared to mice that are healthy. Together, they suggest the living contents of our digestive system may play a surprisingly large role in our mental health.

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